Oddities, musings and news from the health world

Rodent of the Week: Secondhand smoke damages liver

September 11, 2009 | 1:00
pm

The dangers of inhaling secondhand smoke are accumulating. A study published today in the Journal of Hepatology found that long-term exposure to secondhand smoke can cause nonalcoholic fatty liver disease in mice.

Fatty liver disease -- which is an abnormal buildup of fat in the liver -- is a growing problem in the United States. It can be caused by chronic, heavy drinking. But in nonalcoholics, it's most often linked to obesity. The condition can lead to liver dysfunction and is thought to contribute to metabolic syndrome and cardiovascular disease.

Researchers at UC Riverside exposed mice to secondhand cigarette smoke for a year in the lab. They found the smoke affected two key substances that regulate fat metabolism. The smoke inhibited the activity of a kinase (adenosine monophosphate kinase) which then caused an increase of a protein called sterol regulatory element-binding protein that leads to more fatty acid production in the liver.

Identifying these two molecules could give researchers new targets to develop drugs that can reverse fat buildup in the liver, said the lead author of the study, Manuela Martins-Green.

More studies are needed to confirm the relationship between tobacco smoke and liver injury in humans, said Drs. Arian Mallat and Sophie Lotersztajn, in an editorial accompanying the study.

[F]indings from a large survey of U.S. adolescents indicate that passive and active smoke exposure are strong independent predictors of the presence of the metabolic syndrome. These observations indirectly suggest that tobacco use may indeed enhance non-alcoholic fatty liver disease, the hepatic hallmark of the metabolic syndrome.

People with fatty liver disease should stop smoking and avoid secondhand smoke, they said.